HUMANE SACRIFICE – EUTHANASIA

The animals whose welfare would be compromised should be sacrificed. Euthanasia is the act of humanely sacrificing animals by methods that induce rapid unconsciousness and death without pain or distress. The use of inappropriate methods for sacrificing an animal can cause significant pain, distress and suffering to the animal. The level of competence of the person carrying out the euthanasia is very important. Animals should be sacrificed only by a trained and competent person using a method that is appropriate to the species.

Euthanasia may be planned and necessary at the end of a protocol or as a means to relieve moderate or severe pain, suffering, distress or lasting harm that cannot be alleviated by analgesics, sedatives, or other treatments.

Criteria for euthanasia include protocol-spe­cific endpoints (such as degree of a physical or behavioral deficit or tumor size) that will enable a prompt decision by the veterinarian and the inves­tigator to ensure that the endpoint is humane and, whenever possible, the scientific objective of the protocol is achieved.

Methods of sacrificing animals should be approved by the IACUC.

Euthanasia should be performed by trained personnel and death must be confirmed by personnel trained to recognize cessation of vital signs in the species being euthanized.

Euthanasia methods can be unacceptable, acceptable or acceptable with conditions. Methods acceptable with conditions can be used in animal research provided that certain conditions, such as weight limit, existence of equipment or training of personnel, are met. Acceptability of a method is specific to the species and age of the animal. For example, cervical dislocation is acceptable only for rodents and rabbits weighting less than 1 kg and those over 150 grams should be sedated. Neonate rodents are resistant to carbon dioxide, so other methods should be used.

Euthanasia can be performed using chemical agents or physical methods. Chemical agents may be injected or inhaled. Use of chemical agents is preferable to physical methods.

Inhalant agents are either compressed gases (typically carbon dioxide) or anesthetics that are administered at a high concentration to induce hypoxia (oxygen starvation). These anesthetics are rapid evaporating liquids, generating a gas or vapor. Breathing the gas, the animal loses consciousness, just as it would in preparation of a surgical procedure. Overdose of the gas causes hypoxia, the cessation of breathing and heartbeat, and brain death.

Inhalant agents may be administered to animals individually or in groups, in a euthanasia chamber. Rodents can be euthanized by using an overdose of inhalant anesthetic in a bell jar, clean glass or plastic chamber with a reservoir and wire mesh on the bottom. A cotton ball is soaked with the anesthetic and placed below the wire mesh, out of reach of the animal. This procedure should be conducted in a fume hood to protect the personnel from breathing the anesthetic vapors when opening the bell jar to remove the carcass.

Overdoes of volatile anesthetics such isoflurane or its equivalents may be used for euthanasia in the induction chamber of an anesthetic machine. The animal is placed in the induction chamber, which is closed tightly, and the concentration of anesthetic is slowly increased past the level used for surgical anesthesia. Waste gas is drawn into waste collection system, where it is absorbed or exhausted safely. This process is called waste gas scavenging.

Carbon dioxide CO₂ is a gas that rapidly induce loss of consciousness being inhaled in a high concentration. It is one of the most commonly used chemical agents to euthanize rodents and other small mammals in laboratory animal research. It is an effective and inexpensive method, and it poses the minimal risk to the operator. Animals inhaling carbon dioxide lose consciousness due to a reduced oxygen level in the brain and other organs. Compressed gas cylinder and a low-pressure regulator must be used to control the flow of gas. The flow rate should provide for a gradual displacement of 30% to 70% of the air inside the euthanasia chamber per minute for conscious rodents. After the rodents become unconscious, the flow rate be increased to shorten time to death. The CO₂ flow should be maintained for a least 1 minute after the animals cease to breath, to assure death.

Injectable euthanasia agents are generally administered to produce a rapid loss of consciousness followed by death. These are usually solutions containing barbiturates and most of injectable euthanasia solutions are controlled substances that have strict requirements for handling, inventory control and record keeping.

While chemical methods of euthanasia should be used whenever possible, there are cases when physical methods may be needed due to scientific requirements. Physical methods of euthanasia either destroy the brain or stop its functioning. Physical methods may involve the use of equipment to apply or force or a cutting action with speed and precision. Example of such equipment include the use of guillotine device or a captive bolt. Even when carried humanely, physical methods can cause emotional distress in observers.

Cervical dislocation is a physical method that involves the dislocation of the vertebrae in the neck. The spinal cord is quickly separated from the skull, preventing transmission of nerve impulses between the brain and the body. When cervical dislocation is properly done, the animal quickly ceases to breath and the heart stops beating. There may by muscle contractions continuing for some time, causing motion of the limbs. This is a result of an automatic reflex and not the sensation of pain. Cervical dislocation is acceptable with conditions for rodents and rabbits under 1 kg and those over 150 grams should be sedated.

Decapitation is a physical method that involves using a guillotine to sever the head from the body. The guillotine must be cleaned between animals and the blade must be kept sharpened.

After euthanasia is performed, the death must be verified by qualified personnel.

Emotional distress is a normal reaction that can be experienced by the personnel involved in euthanasia procedures. This may lead to difficulty performing the task again, anxiety, depression, loss of interest to work. Co-workers and supervisors should be attentive to the signs of emotional distress.

Animal Care and Use Manual (Annex 2) provides methods recommended by Directive 2010/63/EU of the European Parliament and of the Council for the species commonly used in the Institute’s projects.

Methods of animal sacrifice

1. In the process of sacrificing animals, methods listed in the table below shall be used. Methods other than those listed in the table may be used on unconscious animals, providing the animal does not regain consciousness before death.
2. The sacrifice of animals shall be completed by one of the following methods:

(a) confirmation of permanent cessation of the circulation;

(b) destruction of the brain;

(c) dislocation of the neck;

(d) exsanguination; or

(e) confirmation of the onset of rigor mortis.

Table Animals-remarks/ methods

Remarks:

1. Shall, where appropriate, be used with prior sedation
2. Only to be used in gradual fill. Not to be used for fetal and neonate rodents
3. Only to be used for rodents under 1kg. Rodents over 150g shall be sedated
4. Only to be used for rabbits under 1kg. Rabbits over 150g shall be sedated
5. Only to be used for rodents under 1 kg
6. Only to be used for rabbits under 5kg
7. Only to be used if other methods are not possible